Add primary keys to tables that don't have them

[Jelle-S]

Description

Adds primary keys to tables where they are missing.

In short: Some database systems (like XtraDB cluster) require explicit primary keys for all tables, so this PR adds them to those that are missing them.
See laravel/framework#15770 for a thorough explanation and more context.

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Tested on our environment where the migrations table was missing the id column (shows you we've been using this since at least 2016 😅 ) and with the default database you get when installing snipe it

Checklist:

• I have read the Contributing documentation available here: https://snipe-it.readme.io/docs/contributing-overview
• I have formatted this PR according to the project guidelines: https://snipe-it.readme.io/docs/contributing-overview#pull-request-guidelines
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[snipe]

We actually specifically do not use primary keys other than incrementing ids in Snipe-IT. We used to have them, but they caused HUGE amounts of problems as requirements and systems changed (stuff that used to not be nullable and had no value then became nullable, etc). If it will still work for your use-case without the custom_field_custom_fieldset, we can probably take this though.